Interpretive Summary: 1,4-dimethylenapthlene (DMN) is a natural product from potato that can reversibly inhibit sprouting in tubers. However, we currently do not know how this compound works. In order to identify the mechanisms through which DMN we looked at over 44,000 genes to see which ones were turned on (or increased in expression) or off (decreased in expression) to attempt to understand what physiological processes and signals were altered following DMN treatment. We also compared the changes in gene expression between cold dormant tubers and tubers that were either allowed to initiate growth for three days and those that were allowed to recover from DMN treatment for two days. We determined that DMN treatment prevented cell division and that DMN treated tubers seemed to retain some characteristics of the those that were cold and dormant. We also observed that DMN treatment appeared to alter the way the tubers responded to and transported the plant hormone auxin. Finally, we found evidence that DMN may regulate the growth and flowering gene FLOWERING LOCUS T by impacting the accumulation of a microRNA (miRNA 156). This work provides an indication for how DMN helps maintain potato dormancy during long term storage, and provides some potential new target pathways that may be further manipulated to assist in preventing premature sprouting of stored potato tubers.

Technical Abstract:
The suppression of sprout growth is critical for the long-term storage of potato tubers. 1,4-dimethylenapthlene (DMN) is a new class of sprout control agent but the metabolic mode of action for this compound has yet to be elucidated. Changes in transcriptional profiles of potato tubers treated with the DMN were investigated using an Agilent 44K 60-mer-oligo microarray. RNA was isolated from nondormant Russet Burbank tubers treated with DMN for three days or activated charcoal as a control. RNA was used to develop probes that were hybridized against a microarray developed by the Potato Oligo Chip Initiative (POCI). Analysis of the array data was conducted in two stages: total array data was examined using a linear model and the software limma and pathway analysis was conducted by linking the potato sequences to the Arabidopsis thaliana. DMN elicited a change in a number of transcripts associated with cold responses, water regulation, salt stress and osmotic adjustment. Additionally, repression of auxin signaling and transport were observed in DMN-treated tubers, and connections between DMN treatment and repression of FT through mi156 regulation were indicated. DMN also resulted in a repression of cyclin or cyclin-like transcripts. DMN also resulted in a 50% decrease in thymidine incorporation suggesting a repression of the s-phase of the cell cycle. QT-PCR analysis demonstrated that DMN increased transcripts for the cell cycle inhibitors KRP1 and KRP2. We conclude the DMN results in alteration of genes associated with cold responses and water regulation and maintenance of a G1/S-phase block possibly through the induction of the cell cycle inhibitors KRP1 andKRP2.